Fantastic stuff, cheers for sharing this! I had no idea about this tunnel or the history of Schipka Pass as there's virtually nothing on-line about it! In fact, I think you've just made HG the definitive on-line resource on Schipka Pass!
Wonder how much of it lies behind the stonework blocking the arch? Not a lot I suppose.
Never knew about the proposed road north of Gallowgate (that would have relegated the ancient road to a minor street!) either!
Thankyou for making HG that bit more interesting today